1. Field of the Invention
The present invention relates to a dishwasher, and more particularly, to a dishwasher and controlling method thereof. Although the present invention is suitable for a wide scope of applications, it is particularly suitable for switching a passage of water supplied to an upper/lower nozzle using a passage switching valve.
2. Discussion of the Related Art
Generally, a dishwasher is a device for washing tableware in a manner of spraying high-pressure water into a washtub to separate particles such as leftover food attached to a surface of tableware from the tableware.
The dishwasher includes a washtub provided within a case, upper and lower racks slidably loaded in upper and lower parts of the washtub, respectively, and upper and lower nozzles rotatably provided to the upper and lower racks to spray water, respectively.
A sump for collecting the water sprayed into the washtub is provided to a bottom of the washtub. A wash pump for pumping supplied water to the upper and lower nozzles is provided to the sump.
The upper and lower nozzles are connected to the wash pump via upper and lower passages, respectively. Hence, if the wash pump is activated, the water within the sump is supplied to the upper and lower nozzles via the upper and lower passages, respectively. The upper and lower nozzles then rotate and spray the water into the washtub.
A passage switching valve, for turning on/off the upper/lower passage by blocking the upper/lower passage selectively, is provided to a diverging portion between the upper and lower passages.
The passage switching valve is coupled to a motor, which rotates the passage switching valve to selectively block the upper/lower passage.
However, while the wash pump is being driven at a high speed, if the passage switching valve is rotated to switch the passage, noise is caused by the pressure variation generated from rotating the passage switching valve.